For the police officers who responded to a report of shots fired inside an Indiana supermarket Wednesday night, their training wasn't what it used to be.

But that was the point. A recent change in training meant the supermarket was cleared "in a matter of seconds," and within a few minutes "they found the suspect, and they ended the attack," according to the Indiana State Police.

Though two people were killed by the gunman inside that Elkhart, Ind., store, more bloodshed was averted.

"The old system used to be to show up, secure the scene, wait for the SWAT team to show up," Indiana State Police Sgt. Trent Smith said at a news conference today. That "usually ended up as more loss of life because you had somebody with a knife or a gun or bomb in a business, in a school, wherever it was at, running rampantly, doing whatever they want."

After the massacre at Columbine High School in 1999, law enforcement officials "realized there needed to be a change," Don Montague, the executive director of the Advanced Law Enforcement Rapid Response Training Program at Texas State University, told ABC News.

And now that the pace of active shooter incidents has tripled in recent years –- particularly since the horror at Sandy Hook Elementary School in Newtown, Conn., more than a year ago –- the FBI is taking Montague's program across the country.

"This is an emergency," Ron Hosko, the head of the FBI's criminal division, told ABC News.

A mass shooting "could happen not only in any town in the U.S.A., but in 'Your Town, U.S.A.,'" Hosko said. "In these cases, every second counts. Any second of delay is a second where a defender can fire off multiple rounds from a hand gun."

The Newtown shooting "galvanized the federal response," Hosko said. Within weeks of the shooting, the White House announced a major effort "to better protect our children and our communities from tragic mass shootings."

In the past year, calls to pass relevant legislation have failed, but agencies like the FBI and Department of Homeland Security have surged efforts and resources toward the issue.

Among its actions, DHS has conducted hundreds of site security assessments at schools and houses of worship. Plus, more than 9,700 people have participated in "active shooter workshops" across the country, and more than 286,000 have taken the DHS "Active Shooter: What You Can Do" course, according to an official.

What's more, in November alone, DHS and the FBI completed 56 regional table-top exercises with private security officials and first responders.

After all, when a gunman is actively shooting, it's up to the first responders -- not necessarily tactical operators -- to end the violence.

"Trust your training, trust your training," Montague emphasized. "Because when you get in that situation, you don't have time to think, and that's what's so important about this training."

But the training is sometimes unnatural for police officers.

"It's hard to walk past [a] door as a police officer unless you're 100 percent sure that there's no bad guy going to come out and get me," Kevin Nichols, an adjunct professor with the ALERRT program, recently said. "But in a situation where you have somebody actively shooting or actively killing people, we have to do that. We have to put ourselves in harm's way for that."

Several police officers who recently trained with Nichols at an abandoned schoolhouse outside the nation's capital agreed.

"I think the most difficult thing is to get through the mass chaos ... and to push yourself to keep going forward to stop threats, to minimize the amount of damage that someone is going to do," said Robert O'Donoghue, an officer in New Jersey.

But training helps officers know what to do, and that's exactly what happened Wednesday night in Indiana when police arrived on the scene, according to authorities.

"There's no doubt in my mind after watching the video that [they had] been well-trained, no doubt whatsoever," Smith said. "Those officers were professional. ... From the time they entered the store and the shooter is subdued is probably one minute or so."

Since the ALERRT program was first developed in 1999, more than 60,000 officers have been trained by it. Other nationwide programs offer similar training. The Justice Department's Bureau of Justice Assistance has given the program a funding boost to expedite training of state and local law enforcement officials.